1. Field of the Invention
The present invention relates generally to bandsaw machines having a flexible bandsaw blade trained around a plurality of wheels or pulleys to perform cutting operations and, more particlularly pertains to methods and apparatus for controlling the feeding of the bandsaw blade into workpieces to be cut in bandsaw machines.
2. Description of the Prior Art
The prior art concerning the present invention will be described, by way of example, about what is called a horizontal bandsaw machine, although the present invention is applicable not only to horizontal bandsaw machines but also to vertical bandsaw machines.
As is well known horizontal bandsaw machines comprise a base on which a workpiece or workpieces to be cut are to be placed and clamped and a cutting head assembly in which a flexible endlesss bandsaw blade is trained around a pair of wheels or pulleys, one of which is power driven to drive the bandsaw blade. In the cutting head assembly, the bandsaw blade is slidably held and guided with its cutting edge facing perpendicularly downwardly by a pair of guide means at the cutting zone where cutting is performed so that it may cut into the workpiece to be cut. The cutting head assembly is so arranged as to be raised away from and lowered toward the base by a hydraulic motor around a hinge pin or along one or more vertically disposed quide means. Thus, in each cutting cycle, the cutting head assembly is firstly raised and then lowered toward the base so as to enable the bandsaw blade being driven therein around the wheels to cut the workpiece which has been placed and clamped on the base.
In conventional bandsaw machines of the above described construction, a problem has been the fact that the bandsaw blade will be often deflected by the cutting resistance bacause of its flexible nature and will not cut into workpieces to be cut. The bandsaw blade will be deflected especially when cutting difficult-to-cut materials such as stainless steels and metal alloys which are generally hard and tough and are mostly subject to work hardening. When the bandsaw blade is deflected and cannot cut into workpieces, it will slide on the workpieces to be cut only to scratch them without performing any cutting, action with a result that a hard layer will be produced in kerfs of the workpieces because of work hardening. Such disadvantages with the conventional bandsaw machines will not only result in a lower cutting rate and a poor cutting accuracy but also will cause a short life of the bandsaw blade and a larger vibration and noise during cutting operations.
In order to solve the problems, the inventor invented a cutting method and apparatus in which the bandsaw blade will be intermittently fed and stopped from feeding into workpieces to be cut. In this arrangement, the bandsaw will be instantaneously stopped from feeding into the workpieces to be cut and then it will drastically into workpieces. Accordingly, the bandsaw blade will be effectively fed with impact into workpieces to be cut with a larger feeding force without scratching them even when cutting difficult-to-cut materials such as stainless steels and metal alloys which are subject to work hardening. However, it is disadvantageous that the bandsaw blade will be fed into workpieces to be cut with too large a feeding force and therefore each tooth of the bandsaw blade will be overworked under the too large feeding force and will be liable to brake. Also, since the bandsaw blade is mostly hydraulically controlled, it is further disadvantageous that shock waves in the hydraulic circuit have a harmful effect on the hydraulic equipment.